Damage Potential of Grasshoppers (Orthoptera: Acrididae) on Early Growth Stages of Small-Grains and Canola Under Subarctic Conditions

Abstract

We characterized the type and extent of grasshopper injury to above- and below-ground plant parts for four crops [barley (Hordeum vulgare L.), oats (Avena sativa L.), wheat (Triticum aestivum L.), and canola (Brassica campestris L.)] commonly grown, or with potential to grow, in central Alaska. Cages were placed on 48 pots containing plants in second to third leaf stages and stocked with 0, 2, 4, and 6 first-instar Melanoplus sanguinipes F. pot(-1). Plants were harvested 22 d after planting. Stem growth of barley and oats was not affected except at the highest grasshopper treatment. In canola, stem biomass was reduced at the medium and high grasshopper treatments, when most of the leaves had been consumed. The highest grasshopper treatment reduced leaf area in barley and oats by approximately 55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41-72%). Wheat and canola plants were smaller than barley and oats across all treatments and, at the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley and oats were reduced by 20-28% again at the highest grasshopper density, whereas the reduction for wheat and canola ranged from 50 to 90%. There was little or no difference among all grasshopper densities for C-N ratio in leaf and stem tissues of all crops. The results suggest that wheat and canola are more susceptible than barley and oats and that densities > or = 2 pot(-1) (approximately > or = 50 m(-2)) of even very small grasshoppers could cause significant damage in small-grain and oilseed crop production.

Growth and yield of barley in relation to grasshopper feeding damage

“…Mukerji et al (1976) and Olfert and Mukerji (1983), studying the effect of severe, short-term defoliation of wheat by grasshoppers, determined that, in general, earlier defoliation had a greater effect than later defoliation events. In light of our study, it appears that timing of initiation of defoliation is not as important when defoliation is gradual, except at very early stages when the aboveground plant tissues may be completely consumed by large numbers of young grasshoppers (Begna and Fielding 2003). In the current study, the grasshoppers were small (3rd instars) when introduced.…”

“…1 and 2, respectively; and, in the field experiments, slopes were 1.9 and 1. 4, in 2002and 2003, respectively (Begna and Fielding 2005.…”

“…Damage occurs most frequently on grasslands, although crops, particularly young seedlings of cereals, are very susceptible (Begna and Fielding 2003). The degree of damage inflicted on crops by grasshoppers depends on many factors, such as number of grasshoppers, their size and feeding rate, weather conditions, and plant vigor.…”

“…In studies of defoliation of small grains, the most common treatment is a one-time defoliation (Ryle and Powell 1975;Mukerji et al 1976;Olfert and Mukerji 1983;Sharrow 1990;Begna and Fielding 2003). One-time defoliation may mimic the effects of a sudden influx of adult grasshoppers, which are then chemically controlled.…”

Sustainable Agriculture for Alaska and the Circumpolar North: Part III. Meeting the Challenges of High-Latitude Farming

“…Grasshoppers are pests of small grains, especially barley and canola (Begna andFielding, 2003, 2005). Costs of insecticide application in Alaska have been estimated at 32.00 U.S. dollars/ha (Begna and Fielding, 2005), making chemical control of grasshoppers costprohibitive except in extreme cases. Prevention or at least minimization of outbreaks is much more economical and environmentally desirable than controlling outbreaks.…”